Structural system



May 30, 1939. 5.1 VON HEIDENSTAM 2,160,791

STRUCTURAL SYSTEM Filed -Nov. 24, 19:57 -2 Sheets-Sheet 1 Iii .1a

% W M V /45 3 M w- 5 J Van y 1.939; E. J. VON HEIDENSTAM 2,160,791

STRUCTURAL SYSTEM Filed Nov..24, 1957 2 Sheets-Sheet 2 Patented May 30, 1939 PATENT OFFICE.

STRUCTURAL, SYSTEM Erik Johan von Heidenstam, Stockholm, Sweden Application November 24, 1937, Serial No. 176,386

. In Sweden November 25, 1936 '23 Claims.

The present invention refers to such building structures, intended particularly for bridge and roof structures, which consist of an arch (or frame) with one or more tie membersand with braces arranged between the arch and the tie member.

by their great capacity to take up a load evenly distributed over the whole span. It is also known that in unfavorable cases of loading, for instance in cases of snow loading or other loading of the one half of the span, for example, the arch will be subjected to pronounced deformations. The bending moments then produced in the arch will as a rule be decisive forthe dimensioning of the structure.

The invention has for its main object to provide such a structural system with an arch and with a tie member or tie .members that if the same, for instance on its having been unloaded, is subjected anywhere to a small or great load, this will immediately cause forces which effectively counteract the deformation of the arch.

Another object of my invention is to provide a brace system cooperating with the arch and the tie member in such a mannerthat the resulting construction will be very rigid and the bending moments arising in the arch very considerably reduced.

With these and other objects in view the invention will be described more closely hereinbelow with reference to the accompanying drawings illustrating embodiments of structures constructed according to the system. In the various figures, the same reference characters have been used to corresponding parts.

Fig. 1 shows an arch having a tie member and a brace system comprising two broken arches of braces, hereinafter called brace polygons, cooperating with the arch andtie member. Figs. 1d. and 11) show details.

.Fig. 2 shows aconstruction similarto that in Fig. 1 but adapted to' serve as abridge.

Fig. 3 shows a construction similar to that in Fig. 2 but having an additional pair of brace polygons.

Fig. 4 shows a modified construction which in addition to the braces has a strut arranged between the arch and the tie member. Figs. 4a. to 402 show details of this construction.

Fig. 5 shows a structure similar to that shown in Fig. t but is intended as a bridge structure.

Figs. 6 to 14 show structures wherein the arch proper has a concave breaking point, that is a breaking point departing from the usual curva- As is well known, arch structures of, this kind when suitably formed are distinguished ture of the arch and directed towards the ti member. All structures shown in these figures are provided With brace systems according to the invention.

Figs. 15 to 18 shown in Fig. 14.

For the sake of simplicity the major part of the embodiments have been shown schematically in a simple way, only the embodiments shown in Figs. 1, 4 and 14 being illustrated more in detail 10 to serve as examples. It is to be understood, however, that the invention is not limited to the use of any special material for the structures in question or to any special method of connecting the various members. 15

In Fig. 1 the arch l is provided with a tie member broken at point 4 and consisting of two parts. 2 and 3. The breaking point 4 is connected with ,the arch by means of two rows of braces 22 and 23 each consisting of a plurality of braces 22a to 22c and 23a to 23c forming angles with each other. In the following the broken arches of braces thus formed will be called brace polygons. They are typical tensional members. At their breaking points the brace polygons are secured to secondary braces il which in this case form vertical suspension rods. In the example shown these suspension rods do not carry any directly loaded part and for this reason they terminate at the brace polygons 22 and 23. The rods ll may therefore be regarded as pertaining to the tensional members of the system.

Fig. 1a which illustrates the joint at the left end of the arch shows that the arch consists of a broad-flanged rolled girder l towhich is welded a 5 gusset 1' which, in turn, is welded'to the part 2 of the tie member. At the breaking point 4 shown in Fig. 1b the parts 2 and 3 of the tie member as well as the braces 22a and 23a and the suspension rod l l are connected by means of a gusset 8, preferably also by welding. Since the parts 2, 3, ll, 22 and 23 are all tensile members'they may preferably consist of round iron bars. The structure shown in Fig. l is primarily intended for halls or the like with a great span.

The camber m of the breaking point, that is to say the level thereof above the connecting line between-the ends or bearings of the arch, is determined by the shape of the arch, the r0 span, the rise of the arch, the position of the 0 points of attachment of the braces and by the values of the dead load and the movable load, in a manner such that bending moments produced in the arch will be reduced as far as possible 55 show details of the structure for the most dangerous or commonest cases of loading.

At a load (primary load) applied for instance to the left portion of the arch, this portion will be depressed in the ordinary way with a corresponding bulging of the right portion of the arch. The brace polygon 22 and the secondary braces or suspension rods l l belonging thereto will thus become unstrained, since they are pure tensional members without any appreciablacapacity to take up pressure. The loading of theuarch also entails an increased tensile stress in the tie member, and if the brace polygon 22' is unstrained, the tensile stress in the part 2 shall thus be balanced by the tensile stresses in'the brace polygon 23, the suspension rods H belonging thereto and the part 3. This consequently has the effect that the brace polygon 23 and its suspension rods will load the arch in its right portion, and this load (secondary load), which obviously will be greater the greater the primary load is, tends to counteractthe bulging of the arch in the right portion thereof. The system thus acts as a so-calledvariable system which in this connection chieflymeans that when the arch isloaded (primary loading), for instance by means of a movable load on the roadway of a bridge, one or more of the braces will bring about a secondary loading of the arch, which counteracts the deformation of the arch on account of the primary load. JBy-the combination of the broken tiemember with the variable system it has thus been brought about that the breaking point 4 may practically be considered as constituting a fixedpointgrelaa tively to which the arch is retained, whereby its deformation is reduced. It is obviousalso that theback strain obtained through the-tensile stress in the brace polygon 23wi1lj beefiective already at a small primary load and becomes operative as soon as the archshowsa tendency toward deformation. The system will be very rigid, and by the fact that the bendingmoments in the arch areappreciably reduced, the latter may be dimensioned considerably lighter than is the case in the hitherto practisedsystems of anything like a similar appearance.

Fig. 2 shows a development of thesystem according to Fig. 1 as applied to a bridge. The tensional members 22 and 23 are arranged here in the same manner as in Fig. hand are secured to the suspension rods H, but the latter extend down to and carry the bridge roadway l0. 'When a movable load is applied to the bridge roadway, the load is transferred-by the'suspension "rods and will cause such conditions-'ofstress-in the tensional members Hand 23 as have been described in connection with'Fig. 1.

When applying the constructionto bridges where the roadway has a certain dead weight, itis suitable to make: the structureso thataits dead load causes immaterialmomentsgin the arch only. To achieve this object the brace polygons (compare Fig. 2) shouldas a-rule:be subjected to tension when the structure'isbeing erected. If in this case the structure loaded by, its. dead Weight only issubjectedafoit instance, to a'movableload on theJeft half. thereof,.:this entails that the stress in the: leftbrace;polygon will be reduced-or entirely caused to .;cease whereas the stress is increased in the; rightbrace polygon. The system will thus-be:operativesinza very favourable way,.in that amovableloadon theleit side, for example, .will-reduceetheyload ,on the left brace p0lygon1loading the :arch, but

will increase the load on the right brace polygon loading the arch, or, in other words, the load on the arch is reduced where the arch is normally apt to be pressed inwardly, and is increased where the arch is normally apt to bulge. In the embodiment according to Fig. l, the brace polygons may also be strained from the beginning, which, in principle, entails the same eiTect as described in connection with Fig 2.

What has been stated above with reference toFigs. 1 and 2 regarding the mode of opera tion of the system also holds true for the em- .:-bodiment according to Fig. 3, which shows a further development of the system according to *Figsf'l and 2. According to Fig. 3, two broken -,-tensional-members-24, 25 and 26, 21, respectively, are provided, which, the same as in the con- 'struction just described, form broken arches and are connected to the suspension rods H at the points of intersection with these rods. The two pairs of brace polygons are displaced relatively -to each other within each pair, so that their top -D0ints do not coincide.

This system involves the advantage that the system is rendered still more rigid atan unevenly'distributed load, which will -beconceived'in'accordance with the abovefrom the fact that with a onesided, unevenly distribwithin that portion where the load is most heav ily concentrated. Here, too, it will be found suitable to have the braces put under tension when they'are fixed in their places. The system is particularly suitable foilarge spans.

As a consequence of the above, the invention also relates to a method in the constructing of structures accordingto the foregoing, particularly according to Figs. 1, 2 and 3. -consists substantially in that, after the arch, the tensional members, the tie members and any suspension'rods'and the roadway have been arranged in their places, the tie members and tensional members are subjected to initial tensile stresses of such magnitude that a suitable stress isimparted to the arch, or the arch is made practically free from moments relative to the deadweight of the structure or to the commonest cases of loading, whereupon the tie and tensional members are definitely secured while this initial stress is maintained. The initial stresses, which thus have'the effect described in the foregoing, may beproducedin any suitable manner, for instance by means of hydraulic jacks or the like.

"It has been stated in the foregoing that the braces are constituted by tensional members, and that one ormore of such tensional members extendjfrom the breaking point of the tie member. Itis feasible, however, also to make the braces mediating the secondary load, or certain of these braces-as compressional members. In such a case it may become necessary to make the ,tie member rigid, for instance by making the same or certain parts thereof as latticeworks.

The structural system as described may be applied to 0, land multi hinged arches of arbitrary form provided with a tie member which is saddle-backed, if desired, and the system is not limited to constructing the arch from a certain The method This is of great imgons 35 and 36.

portance, particularly in concrete structures, also from the point of View that hereby facilities are provided to cause the cross sections of the arch to be pressed over the whole surface, which entails-in addition to a lessened dead weight and a reduced consumption of material-an increase of the safety against buckling. Through the invention, it will be possible, furthermore, in a number of cases to employ externally statically determined systems to economical advantage, such systems showing constructively good properties, for instance with respect to reactive forces and to temperature and shrinkage stresses.

As will be found from the foregoing description, the expression variable system must not be construed as involving that certain braces must under all circumstances be rendered inoperative, that is to say be unstrained, for this is of course a matter which depends on the application and the magnitude of the'load. The expression involves that this tendency and possibility of being rendered inoperative is present, although in a certain case of loading the braces are not perhaps unstrained.

Fig. 4 shows an arch l with a tie member 2.

Extending from the middle point 30 of the arch is a compressional strut 3| to a point 32 at the center of the tie member. This point 32 is connected with the end points 33 and 34 of the arch, respectively, by means of brace polygons 35 and 36, each consisting in the example illustrated of six members. The arch I is broken in correspondence to the brace polygons, and arranged between the breaking points of the arch and the breaking points of the polygons are a number of secondary braces H. Moreover, the end points of the arch are connected with the middle point 38' by means of obliquely directed braces 31 and 38, which between their end points are also con nected with the arch by means of compressional braces, 39. These compressional braces 38 are preferably disposed in such places where there are breaking points in the arch and the brace polygons, so that these braces may serve both as compressional members between the arch and the oblique braces 31, 38 and as tensional members between the arch and the brace poly- Examples of this are shown, inter alia, in the two central compressional members 39, which are continued beneath the oblique braces 37 and 38 directly by the tensional members H. The members ll and 38 may, for the sake of simplicity, be commonly termed the vertical braces, although they need not necessarily be vertical. Thus, for instance, the compressional members 39 may be positioned at right angles to the arch section in question.

Fig. 4a shows the joint of the various members at the left end of the arch. Also in this instance, the arch consists of a broad-flanged girder to which the members 2, 35 and 31 are connected by means of a gusset i. Fig. 4b shows that the braces 31, 38 and the strut 3! are connected to the crown 30 of the arch by means of a gusset la. Fig. 40 which is a section taken along the line c-c in Fig. 4b shows that the strut 38 may consist of two U-irons. Fig. 411 shows the connection at the middle point 32 of the tie member by means of a gusset 8.

'The structure shown in Fig. 4 is operative in the same manner as described in connection with Figs. 1 to 3 but in addition hereto the members 31 and 38 will come into action as follows.

If the left half of the bridge in the figure is loaded by means of a movable load while the right half remains unloaded the oblique brace 31 is brought under a tensile stress, whereas the oblique brace 38 slackens or is subjected to compressive stress. From this point of view, the oblique braces 37 and 38 may be made so as to be able also to transfer pressure. The tensile stress in the oblique brace on the primary loaded side corresponds to an increase of the pressure in the arch in the most heavily loaded portion of the arch due to the unevenly distributed load.

If the dead load be disregarded, the structure will thus act theoretically as a Variable system as previously described. The structure is well stiffened, the bending moments are materially reduced, and the buckling risk for the loaded portion of the arch is greatly reduced, which is all the case also in regard tothe embodiments to be described in the following.

If it is desired to load thetie member, it may be found suitable in the embodiment shown in Fig. 4 to cause the suspension rods H or certain ones of the same to extend down to the tie member so as to carry the latter. The tie member may then, for instance, be made as a girder and i be employed for the carrying of cross bars, telfer carriages or the like. This is also the case with the embodiments described later on.

The structure shown in Fig. 5 corresponds broadly with that shown in Fig. 4, but is intended as a bridge structure, the bridge roadway It being carried by the suspension rods. It is preferable here to make the bridge roadway as a tie member. The structure may also be brought into use, if in place of a bridge roadway it is desired to cause the tie member to carry some other heavier load. I

Fig. 6 shows an embodiment, which in regard to the tie member 2, the compressional member 3!,

the brace polygons 35 and 38 and the braces I! corresponds to the structure disclosed in Fig. 4. Differing from the latter structure, however, the arch is in the present case broken in a concave manner, that is to say broken inwardly in a direction toward the tie member, the breaking point 43 being connected with the tie member by means of the strut 3|. The mode of operation of the structure corresponds in principle to what has been previously described. Through this construction it will be possible also for great onesided loads to make the arch practically free from moments, and such as to have substantially only to take up normal forces.

In the embodiment shown in Fig. 7, there is again the arch broken in a concave manner, the breaking point of which is connected with the tie member at the point 32 by means of the strut 3|. In this case, however, each half of the arch shows two brace polygons 43, 44 and 45, 46, respectively, which at their breaking points are connected to the suspension members I l. Besides, the brace polygons are connected with each other at their points of intersection 41, 48.

All of the embodiments above described may be employed in connection with broken tie members in the manner described in connection with Figs. 1 to '3. Examples of app-lying the present invention to structures having a broken tie member are illustrated in Figs. 8 and 9.

The structure shown in Fig. 8 thus has an arch 5 broken in a concave manner and brace polygons 35 and 35 of the kind previously described. The tie member 2 is broken, however, as will be seen from the figure, and the strut 3| connects the breaking point 32 with the breaking point 49 of the arch.

The embodiment according to Fig. 9 corresponds to the structure shown in Fig. 8, with the difference that it is intended as a bridge structure' The bridge roadway N), which may extend above, below of through the breaking point 32, is carried here-by the extended suspension rods H.

The following Figures 10 to 14 show embodiments-in whichthe oblique braces 31, 38 described in connection with Figs. 4 and are employed in arches having a concave breaking point.

In Fig. lO'the braces 31 and 38 are broken and connect the ends of the arch with the crown. At

their breaking points, these braces are connected with the arch by means of the secondary braces H. The braces 37 and 38 aid toward stifiening the arch further, and in neutralizing or counteracting the tendency thereof toward lateral displacements from the loaded side. Such a tendency may involve, for instance, that when the left side of the arch in the figure is primarily loaded, the crown 49 tends to move to the right. This -is-counteracted by the brace 31, which is subjected to tensile stresses and produces a hack strain at the point til increasing with the load.

Fig. 11 shows an embodiment, wherein the braces -3land 38 are constructed broadly in the same manneras according to the preceding figures. The-brace polygons 35 and 36,-on the other hand, -are'at their inner portions, that is to say adjacent to thecenter of the arch, straight for a greater length and not connected with the arch by means of secondary braces. For the stiffening of the inner portions of the arch, there are arranged combined braces 59 and 50, which are connected with the-braces 31 and 38, respectively, as well as with the arch. Otherwise, the arrangement is operative in the same manner as the arrangement according to Fig. 10.

In the embodiment according to Fig. 12, the braces El and 33 are straight, whereas the brace polygons -35 and 36 are arranged 'in the same manner as in Fig. 10. Tensile members 5! and 52 extending from the point 32 are connected with the braces 31 and 38, respectively, and also, by means'of vertical braces, with the arch to stiffen the inner portions thereof. The dotted lines 53 indicate that the vertical braces may be made as suspension members and carry a bridge roadway or other-load on the arch. This possibility is also present in the embodiment shown in the remaining figures.

In the embodiment according to Fig. 13, the braces '37 and 38 are also straight. To stiffen the inner portions of the arch, special tensional members 54, 55 are connected with the brace polygons 35 and 36 and with the braces 37 and 33, from the connecting point of which tensional members with the braces 3'! and 38, respectively, vertical. bracesi56, 51 extend to the arch. These braces 5 and 51 are furthermore connected with the polygons 35 and 36 at breaking points 58, 59 of the same.

In-the embodiment according to Fig. 14, the braces 31, 38 are shown as being straight. The brace polygons, on the other hand, are of a construction differing from the embodiments shown in Figs. -13, in that there are provided two different brace polygons within each half of the arch, that is to say one, the various members of which are designated by a, b, c, d, and a secend, the various parts of which are denoted by e, f, g. The member a may at the same time form the outer portion of the brace 31 extending between the end of the arch and the crown 40. The brace polygons are in a manner previously described connected at their breaking points with the arch by means of secondary braces. Now, the two brace polygons a--d and 6 9 are at a point above their common point of intersection 60 connected by means of a bonding brace, i. e. a broken brace Gla, Gib in the case illustrated, the'breaking point of which is likewise connected with the arch and with the point of intersection of the brace polygons, besides which the end points of this brace are connected with the arch by means of vertical braces. This bonding brace, which may be straight between its ends located on the brace polygons, makes it possible that the resultant of the brace system on the least loaded side may take a position nearer to the arch than would be the case, if this bonding brace were lacking. The inner end point of the bonding brace (ii is located on the brace 31 connecting the end of the arch with the crown, as will be seen from the figure.

With the exception of the strut 3! all members below the arch in Fig. 14 are tensional members although as a tie member there is used a double T-iron. This is for the purpose of letting the tie take up a direct load, such as transversing telfer carriages. For this purpose the vertical braces extend down to and are connected with the tie member.

Fig. shows the joint at point 32. To the tie member 2 there is welded a gusset plate 62 which, in turn, is connected with the inner ends d and e of the brace polygons. Likewise the strut 3! is connected to the gusset 62. As shown the strut is formed by a broad-flanged girder but instead two U-irons may be used. The construction shown in Figs. 14-18 is a roof truss and is an example taken from practice. To secure the different trusses laterally I employ a tube 63 which extends through the several joints 32 of the trusses and is rigidly connected with all such joints. Fig. 16, which is a section along line 5-46 in Fig. 15. shows how the tube 63 extends through the gusset 62.

Fig. 1'? shows the joint at the crown v40 of the arch. The broad-flanged girders la and lb forming the arch are cut off and welded end to end as indicated at 64. Further, these ends are connected by means of a gusset 65 which is also connected to the strut-3| and the braces 31, 38. From Fig. 1'7 and Fig. 18, which is a section along line iii-l8 in Fig. 17, it can also be seen that between the flanges of girder la there are arranged stiffening plates 66 to keep said flanges from bending owing to the pressure from strut 3!. The joint thus formed is extremely strong and rigid. Of course, I do not limit myself to the use of welding for connecting the various members together.

It holds good in regard to all of the structures shown that they may, theoretically and disregarding their dead weight, be considered as variable systems. In all cases, the arches may be made either as continuous curves, or be composed of more or less straight parts which together approach the arcuate shape, although showing breaking points. Forms with more than one concave breaking point are also conceivable.

Furthermore, embodiments may be conceived that have single braces or brace polygons extending from more than one point of the tie member. The braces also need not necessarily extend from the ends of the arch, but may be secured in the proximity of "these ends, for instance somewhat higher, so that a portion of the end of the arch maybe regarded as the final brace or be considered to serve as such. Moreover, the brace polygons and the tensional members may, instead of extending from the connecting point between the strut and the tie member, extend from this strut somewhat above the point. Finally, the tie members may in all embodiments be elevated, so that the springers will be located beneath the same, that is to say beneath the ends of the arch proper.

What I claim is:

1. In a structural system comprising an arch and a tie member, said tie member being broken in consisting of two parts forming an angle with eachother, the point of said angle being directed against the arch, at least two brace polygons, each consisting of a broken arch of braces, provided between the arch and the breaking point of the tie. member, and secondary braces connecting the breaking points of said brace polygons.with the arch.

2. In a structural system comprising an arch and a tie member, said tie member being broken in consisting of two parts forming an angle with each other, the point of said angle being directed against the arch, at least two brace polygons, each consisting of a broken arch of braces, provided between the arch and the breaking point of the tie member, and secondary braces connecting the breaking points of said brace polygons with the arch, the various parts being so arranged relatively to each other that at primary loading of the arch the braces bring about a secondary loading of the arch counteracting deformation of the arch on account of the primary load.

3. In a structural system comprising an arch and a tie member, at least four brace polygons, each consisting of a broken arch of braces, provided between the arch and the tie member, a plurality of brace polygons being arranged for each half of the span of the arch, the top points of said brace polygons being displaced relatively to each other in the longitudinal direction of the arch and secondary braces connecting the breaking points of said brace polygons with the arch.

4. In a structural system comprising an arch and a tie member, at least two brace polygons, each consisting of a broken arch of braces, provided between the arch and a common point on the tie member, a vertical member forming a strut connecting said common point with the arch and secondary braces connecting the breaking points of said brace polygons with the arch, additional obliquely positioned braces extending from the connecting point of the arch with said strut to the ends of the arch, said additional braces being arranged at an unevenly distributed load on the arch to take up a tensile stress corresponding to the increase of the pressure in the arch in the part thereof subjected to the heaviest load.

5. In a structural system comprising an arch having at least one concave breaking point and at least one tie member, at least two brace polygons, each consisting of a broken arch of braces, provided between the arch and the tie member, secondary braces connecting said brace polygons with the arch, and at least one strut connected with the arch and cooperating with said brace polygons,

6. In a structural system comprising an arch having at least one concave breaking point and at least one tie member, at least two symmetrically arranged brace polygons, each consisting of a broken arch of braces, provided between the arch and the tie member, secondary braces connecting the breaking points of said'brace poly gons with the arch, and at least one strut connected with the arch and cooperating with said brace polygons, the various parts being so arranged relatively'to each other that at primary loading of the arch the braces bring about a secondary loading of the arch counteracting deformation of thearch on account of the primary load.

'7. In a structural system comprising an arch having at least one concave breaking point and at least one tie member, at least two brace polygons, each consisting of a broken arch of braces, provided between the arch and the tie member, secondary braces forming suspension rods and connecting the breaking points of said brace polygons with the arch, and at least one strut connected with the arch and cooperating with said brace polygons.

8. In a structural system comprising an arch having at least one concave breaking point and at least one tie member, at least four brace polygons, each consisting or a broken arch of braces, provided between the arch and the tie member, a plurality of brace polygons being arranged for each half of the span of the arch, the top points of said brace polygons being displaced relatively to each other in the longitudinal direction of the .arch, secondary braces connecting said brace polygons with the arch, and at least one strut connected with the arch and cooperating with the tie member and the brace system.

9. In a structural system comprising an arch having at least one concave breaking point and at least one tie member, at least four symmetrically arranged brace polygons, each consisting of a broken arch of braces, provided between the arch and the tie member, a plurality of brace polygons being arranged for each half of the span of the arch, the top points of said brace polygons being displaced relatively to each other in the longitudinal direction of the arch, secondary braces connecting the breaking points of said brace polygons with the arch, and at least one strut connected with the arch and cooperating with the tie member and the brace system, the various parts being so arranged relatively to each other that at primary loading of the arch the braces bring about a secondary loading of the arch counteracting deformation of the arch on account of the primary load.

10. In a structural system comprising an arch having at least one concave breaking point and a tie member, a plurality of brace polygons, each consisting of a broken arch of braces, connected to the arch and to a common point on the tie member, a strut connecting said common point with the arch, and secondary braces connecting said brace polygons with the arch.

11. In a structural system comprising an arch having at least one concave breaking point and a tie member, a plurality of brace polygons, each consisting of a broken arch of braces, connected to the arch and to a common point on the tie member, a strut connecting said common point with the arch, secondary braces connecting said brace polygons with the arch, and additional obliquely positioned braces extending from the connecting point of the arch with said strut to the ends of the arch, said additional braces being arranged at an unevenly distributed load on the arch to take up a tensile stress corresponding to the increase of the pressure in the arch in the part thereof subjected to the heaviest load.

' the arch, and at least, onestrut connected with 75 having, a concave breaking point and a tie mem- ,arch and with braces connecting the, breakingv points of said the arch and with the breaking point. of the tie member.

13, In a structural system comprising. an arch having at least one concave breaking point and a tie member, a plurality of brace polygons, each consisting of a broken arch of, braces, provided between the arch andthe ,tie member, a vertical strut connected with the, breaking point of the the tie member, and, secondary brace polygons with the arch.

14. In a structural system comprising an arch having plurality of braces connecting the arch with the connecting point of. saidstrut with. said tie, memerl 5 In a structural systemv comprising. an arch having at least one. concave breaking point and a tie member, a plurality of bracepolygons, each consisting of a broken arch of. braces, provided.

between the arch and. thetie member, a. vertical strut connected with the, breaking point of the arch and with the tie member, secondary braces connecting the breaking pointsv of said brace polygons with, the arch, at least some ofsaid secondary braces forming suspension rods ex tending to, and connected, with the tie member and the tie member being so, arranged that it is capable of taking up additional loads in the form of cross bars or thelike.

16 In a structural system comprising. an arch having a concave breaking point and a tiemember, a strut. connecting the breaking point of the arch with the tie. member, a, plurality, of brace.

polygons, each consisting of a broken arch of braces, connecting, thearch with the, connecting point of saidstrut with the tiemember, secondary braces connecting said, brace. polygons with the arch; and additional, obliquely positioned braces extending from the connecting point of thearch with said strut to the ends of the arch, said, additional braces being arranged at an unevenly distributed load on the arch to take up a tensile stress corresponding to the increase, of the pressure in the arch in. the part thereof subjected to the heaviest load.

17. In a structural system comprising an arch having a concave breaking point and a tie member, a strut connecting the breaking point of the arch with the tie member, a plurality of brace polygons, each consisting of a broken. arch of braces, connecting the arch with the connecting point of said strut with the tie member, secondary braces connecting said brace polygons with the arch, additional, obliquely positioned braces extending from the connecting point of the arch with said strut to the ends of the arch, and further braces extending between the arch and points on said. additional braces, between the ends thereof.

18. In a structural system comprising an arch of two parts forming an angle, with at least one concave breaking, point and. a tie member, a strut connecting the. breaking point of the arch with. said tie. member, and a l2. In a structural system comprising an arch, having at least onev concayebreakingpoint and.

her, a strut connecteditothe breaking point of the arch and tosaid tie, member, at least. two

brace polygons, each.consis ting of abroken. arch.

ber, a strut connected to the breaking point. of

the arch and to said tie member, at least two brace polygons, each consisting of a. broken arch of braces, provided between. the arch'andv the tie member in each half. of. the span. ofthe arch, the toppoints of said. brace. polygonsbein'g'displaced relatively to each other. in. the. longitudinal direction of the arch, a. broken. bonding brace connecting said brace polygons at a point above their, point, of intersection, secondarybraces connecting the. breaking points. of. said. brace polyensv with thearch, and a vertical brace connect.- ingthe breaking point of. said bonding brace with arch.

20 In a, structural system comprisingan. arch having a concave breaking point anda tie memher, a; strut connected, to the. breaking point of the arch, andv to said. tie. member, at. least. two bracepolygons, each consisting of a broken arch of braces provided between the arch and the tie member :in each half of. the spanof the arch, the top points. of said brace polygons being displaced relatively to each other in the longitudinal direction of the arch, a brokenbonding brace connecting. saidv brace polygons at a point above their point of; intersection, secondary braces connecting, the breaking points of said. brace. polygons with thearch, andverticalbraces connecting the ends of said, bonding brace as well as the breaking point thereof with the arch.

21. In a structural. system comprising an arch having. a concave breaking point. and a tie member, a strut connected to the breaking point of the archandto said tie member, at least one. pair oi brace, polygons, each brace polygon consisting of a broken, arch of braces, provided between the.

archand the tie member in each half; of. the span of, thearch, the top. points of the. brace polygons in each pair being displaced relatively to. each other. in thelongitudinal direction, of the arch, a bonding brace. connecting said, brace. polygons of eachpair at apoint above their point of. inter.- section, an additional, obliquely positioned. brace in each half of, the arch extending between the breaking point of the, arch andtheend thereof, the ends of the bonding braces located towards the center. oi the arch being located on said additional braces, and secondary braces connecting the breaking points or said brace polygons with the arch.

22 A method in the construction of a structure having, an arch, a tie member for. said arch, andbraces connecting the arch and thetie member, comprising arranging the arch, the tie member and the braces in their. places, subjecting the tie member. and the braces to initial tensile stresses, thereby imparting stresses to the arch, and definitely securing the tie member and; the braces to one another and; to the arch while maintaining said initial stresses.

23. A method in the construction of a struc 2,1eo,791 r 7 made practically free from moments, and definitely securing the tie member and the braces to one another and to the arch while maintaining said. initial stresses.

ERIK J OHAN VON HEIDENSTAM. 

